HVAC Issue, need ideas where to start

'98 528i

The temp control wheel between the center vents. When turned all the way to the cold position, air flows, no issues. When turned all the way to the warm position, no air flows even when the fan speed is turned all the way up.

I recall once, driving with the AC on, I noticed I wasn't getting cold air coming from the center vents. All of a sudden, I hear a very subtle clunk,pop,thud and then I get a rush of cold air coming from the center vents.

Would this be a "flapper" motor issue or something else??

Looking for ideas of where to start trouble shooting.

Thanks in advance!!

The center wheel is entirely mechanical. If you get a normal cold air flow, but not hot, the cable is either slipped or broken. I've not had mine apart, but you can lever out the center vent. Search here for more info.

I'd start by typing /HVAC F3 in the bestlinks...

For example ...
- How to remove the IHKA air conditioning control panel to clean the circuit board (1) (2) (3) (4) & an HVAC (IHKA) sampling fan check - a cn90 15 min DIY project! (1) & how to remove the trim and bracket holding the MID & HVAC/IHKA panels (1) (2)